Modular core orientation system

ABSTRACT

A core sample orientation system ( 10 ) comprising a first portion ( 11 ) and a second portion ( 12 ). The first portion ( 11 ) comprises a downhole unit adapted to be connected to a core tube of a core drill, and the second portion ( 12 ) comprises a control unit. The downhole unit ( 11 ) is adapted for cooperation with a core tube for recording data relating to the orientation of the core tube, and the control unit ( 12 ) is adapted to cooperate with the downhole unit to receive and process orientation data from the downhole unit and provide an indication of the orientation of a core sample within the core tube at a time prior to separation of the core sample from the underground environment from which it was obtained. The downhole unit ( 11 ) is configured to cooperate with the control unit ( 12 ) to establish an operative connection therebetween. More particularly, the downhole unit ( 11 ) and the control unit ( 12 ) are configured to provide a coupling ( 23 ) for releasably connecting them together in a manner allowing selective rotation therebetween. The coupling ( 23 ) comprises a combination of magnetic coupling and mechanical coupling.

FIELD OF THE INVENTION

This invention relates to core sample orientation. More particularly, the invention relates to a core sample orientation system for providing an indication of the orientation of a core sample relative to the underground environment from which the core sample has been extracted, and also to a method of core sample orientation identification.

BACKGROUND ART

The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

There is a need for core sampling in geological surveying operations.

Core samples are obtained through core drilling operations. Core drilling is typically conducted with a core drill comprising outer and inner tube assemblies. The inner tube assembly is known as a core tube. A cutting head is attached to the outer tube assembly so that rotational torque applied to the outer tube assembly is transmitted to the cutting head. A core is generated during the drilling operation, with the core progressively extending along the core tube as drilling progresses. When a core sample is required, the core within the core tube is fractured. The core tube and the fractured core sample contained therein are then retrieved from within the drill hole, typically by way of a retrieval cable lowered down the drill hole. Once the core tube has been brought to ground surface, the core sample can be removed and subjected to the necessary analysis.

Typically, the core drilling operation is performed at an angle to the vertical, and it is desirable for analysis purposes to have an indication of the orientation of the core sample relative to the underground environment from which it was extracted. It is therefore important that there be some means of identifying the orientation the core sample had within the underground environment prior to it having been brought to the surface.

Core orientation devices are used to provide an indication of the orientation of the core sample. Many of these devices are mechanical in nature.

The applicant's international application PCT/AU2005/001344 (WO 2006/024111) discloses a core orientation device which records orientation information electronically and processes the information to provide an indication of the orientation of the extracted core sample relative to the underground environment from which it was extracted. The device comprises a tool which is adapted to be coupled to the core tube. The tool incorporates means for determining and storing the orientation of the tool at predetermined time intervals relative to a reference time, means for inputting a selected time interval, means for relating the selected time interval to one of the predetermined time intervals and providing an indication of the orientation of the device at the selected time interval, means for comparing the orientation of the tool at the selected time interval to the orientation of the tool at any subsequent time and providing an indication of the direction in which the tool should be rotated in order to bring it into an orientation corresponding to the orientation of the tool at the selected time. Thus the core sample confined within the core tube is brought into an orientation corresponding to its original orientation in the underground environment. The core sample can then be marked prior to being withdrawn from within the core tube.

All componenty required for operation of the device, including sensors, microprocessor, memory, circuitry and associated circuit boards, power supply, keypad and visual display unit (LCD) are incorporated in the tool and so are deployed in the borehole with the tool.

It would be advantageous to isolate some of the componentry from the borehole so that it is not vulnerable to damage arising from the arduous conditions to which the tool is typically exposed while down the borehole.

DISCLOSURE OF THE INVENTION

According to a first aspect of the invention there is provided a core orientation system comprising a first portion adapted for cooperation with a core tube for recording data relating to the orientation of the core tube, and a second portion adapted to cooperate with the first portion to receive and process orientation data from the first portion and provide an indication of the orientation of a core sample within the core tube at a time prior to separation of the core sample from the underground environment from which it was obtained, the first and second portions being adapted for cooperation in a manner allowing selective rotation therebetween.

With such an arrangement, the first portion can be deployed underground with the core tube to record data corresponding to the orientation of the core tube (and any core sample contained therein). Once the core tube, along with the first portion attached thereto, has been retrieved from underground, the second portion can be brought into cooperation with the first portion to receive and process the orientation data received from the first portion. This arrangement is advantageous as it is not necessary for the second portion to travel underground and be exposed to the harsh conditions associated therewith.

Typically, the first portion adapted for cooperation with a core tube by being adapted for connection to the core tube for rotational movement in unison therewith. The first portion may be adapted for connection with the core tube, either directly or indirectly. The first portion may be directly connected to the core tube, typically (although not necessarily) through a threaded connection therebetween. The first portion may be indirectly connected to the core tube by being accommodated within a housing which is connected to the core tube, typically (although not necessarily) through a threaded connection.

Preferably, there is provided a coupling for releasably coupling the two portions together to provide the cooperation allowing selective rotation therebetween. Typically, the coupling is so configured that the second portion can dock onto the first portion. The coupling may comprise a combination of magnetic coupling and mechanical coupling.

In particular, the coupling is configured to allow selective rotation of the second portion relative to the first portion if desired to establish a desired orientation between the two portions.

The mechanical coupling may comprise a spigot formation associated with one of the two portions and a corresponding socket formation associated with the other of the two portions for providing alignment between the two portions when the spigot formation is received within the socket formation.

The magnetic coupling may comprise an attractive force between the two portions for biasing the spigot formation and the socket formation into engagement.

The spigot formation may be provided on the second portion and the corresponding socket formation may be associated with the first portion. In one arrangement, the corresponding socket formation may be provided in the first portion. In another arrangement, the corresponding socket formation may be provided in a member associated with the first portion. The member may comprise the housing in which the first portion is accommodated.

The housing may comprise at least two parts adapted for connection together and selectively separable to provide access to the first portion accommodated therein.

Preferably, orientation data is transmitted from the first portion to the second portion by wireless communication. The wireless communication may comprise infrared (IR) short-range communication. With this arrangement, the first and second portions are each provided with an IR interface to facilitate IR communication therebetween.

It should be appreciated that orientation data may be transmitted from the first portion to the second portion in any other appropriate way, including a physical transmission link established between the first and second portions when they are coupled together.

The first portion may comprise a downhole unit and the second portion may comprise a control unit.

According to a second aspect of the invention there is provided a core orientation system comprising a first portion for recording orientation data and a second portion adapted to cooperate with the first portion to receive and process orientation data from the first portion, the first and second portions being adapted for cooperation in a manner allowing selective rotation therebetween.

According to a third aspect of the invention there is provided a survey tool system comprising a housing and a core orientation system, wherein the core orientation system comprises a first portion for recording data relating to the orientation of a core sample, and a second portion adapted to cooperate with the first portion to receive and process orientation data from the first portion and provide an indication of the orientation of the core sample at a time prior to separation of the core sample from the underground environment from which it was obtained, the first portion being contained within the housing, the housing comprising at least two parts adapted for connection together and selectively separable to permit the second portion to access the first portion for cooperation therebetween.

According to a fourth aspect of the invention there is provided a survey tool system comprising a housing, a downhole unit for recording data relating to the orientation of a core sample, and a control unit adapted to cooperate with the downhole unit to receive and process orientation data from the downhole unit and provide an indication of the orientation of the core sample at a time prior to separation of the core sample from the underground environment from which it was obtained, the downhole unit being contained within the housing, the housing comprising at least two parts adapted for connection together and selectively separable to permit the control unit to access the downhole for cooperation therebetween.

According to a fifth aspect of the invention there is provided a method of providing an indication of the orientation of a core sample relative to a body of material from which the core sample has been extracted, the method being performed using an orientation system according to the first or second aspect of the invention.

According to a sixth aspect of the invention there is provided a method of providing an indication of the orientation of a core sample relative to a body of material from which the core sample has been extracted, the method being performed using an survey tool system according to the third or fourth aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reference to the following description of several specific embodiments thereof as shown in the accompanying drawings in which:

FIG. 1 is a schematic view of a downhole unit forming part of a core sample orientation system according to the first embodiment;

FIG. 2 is a schematic view of a control unit also forming part of the core sample orientation system

FIG. 3 is a fragmentary schematic view of the control unit in operative engagement with the downhole unit;

FIG. 4 is a schematic elevational view of a removable chassis forming part of the control unit;

FIG. 5 is a side view of the chassis;

FIG. 6 is a schematic view of a calibration unit for calibrating the downhole unit;

FIG. 7 is a schematic view of a docking station for the control unit;

FIG. 8 is a block diagram illustrating various components of the downhole unit;

FIG. 9 a block diagram illustrating various components of the control unit;

FIG. 10 is a sectional perspective view of a core sample orientation system according to the second embodiment, with the downhole unit shown accommodated in part of a housing therefor, and the control unit shown coupled to the downhole unit;

FIG. 11 a schematic view of an assembly in which the housing is accommodated and the control unit shown schematically in position in relation the housing;

FIG. 12 a schematic view of one part of the housing, with the other part having been separated therefrom to provide access to a downhole unit accommodated in the first part, and a control unit shown for cooperation with the downhole unit;

FIG. 13 is an end view of the control unit;

FIG. 14 is a side elevational view of the housing;

FIG. 15 is a side elevational view of the housing showing the two parts thereof in a separated condition; and;

FIG. 16 is a sectional elevational view of the housing.

BEST MODE(S) FOR CARRYING OUT THE INVENTION

Referring to FIGS. 1 to 9, there is shown a core sample orientation system 10 according to the first embodiment comprising a first portion 11 and a second portion 12. The first portion 11 comprises a downhole unit adapted to be connected to a core tube (not shown) of a core drill of a type well known in the art. The second portion 12 comprises a control unit, as will be explained in more detail later.

The downhole unit 11 is configured for connection to the upper end of the core tube; specifically, by threaded engagement therewith. When so connected to the core tube, the downhole unit 11 is fixed for rotation with the core tube.

The downhole unit 11 comprises a cylindrical housing 15 having a first end 17, a second end 18, and a cylindrical side wall 19 extending between the two ends.

The side wall 19 has an outer periphery 21 configured and dimensioned to accord with the outer periphery of the core tube.

The first end 17 of the downhole unit incorporates a threaded section (not shown) for threaded engagement with a mating threaded section on the upper end of the core tube.

The downhole unit 11 is configured to cooperate with the control unit 12 to establish an operative connection therebetween, as will be explained in more detail later. More particularly, the downhole unit 11 and the control unit 12 are configured to provide a coupling 23 for releasably connecting them together in a manner allowing selective rotation therebetween. The coupling 23 comprises a combination of magnetic coupling and mechanical coupling, as will be explained.

The coupling 23 comprises a socket formation 25 on at the second end 18 of the downhole unit 11 and a corresponding spigot formation 27 on the control unit 12 for providing alignment therebetween when the spigot formation 27 is received within the socket formation 25. The mechanical connection is established by engagement between the socket formation 25 and the spigot formation 27. The magnetic coupling provides an attractive force between the downhole unit 11 and the control unit 12 for biasing the spigot formation 27 and the socket formation 25 into engagement.

The socket formation 25 has an inner face 31 with a radially outer section 33 which incorporates a magnetic element 35. The spigot formation 27 has an outer face 37 with a radially outer section 41 which incorporates a further magnetic element 43. The two magnetic elements 35, 43 cooperate to establish the magnetic attractive force between the two portions 11, 12 when the spigot formation 27 is received within the socket formation 25.

The control unit 12 comprises a generally circular body 51 having an outer face 53, an inner face 55 and a circular outer peripheral wall 57. The spigot formation 27 is incorporated in the body 51 and projects axially from the inner face 55.

The body 51 is configured so as to be of a shape and size that can be readily grasped and manipulated by hand, even when the operator is wearing protective gloves.

The body 51 has an interior region 61 accommodating a removable chassis 63 which carries a circuit board 65 and related componentry. With this arrangement, either the body 51 or the chassis 63 can be replaced as necessary in the event that any component thereof becomes defective.

The body 51 also accommodates a power supply 67 in the form of a lithium battery pack, and an IR interface 68 which is disposed within the spigot formation 27.

The outer face 53 of the body 51 incorporates an input device 69 in the form of a keypad and a visual display device 71 in the form of a liquid crystal display unit.

The chassis 63 carries a processing means 73 in the form of low power microcontroller, a memory device 75 providing non-volatile memory, a timer 77 and a watchdog circuit 79.

The housing 15 of the downhole unit 11 has an internal cavity 81 which accommodates a module 83 incorporating a triaxial accelerometer means 85, an analogue-to-digital converter 87, a processing means 89 in the form of low power microcontroller, a memory device 91 providing non-volatile memory, a power supply 92 in the form of a lithium battery pack and a watchdog circuit 93. Further, the module 83 is provided with an IR interface 95. With this arrangement, the downhole unit 11 can record data relating to its orientation (and thus the orientation of the core tube to which it is attached). When the downhole unit 11 is retrieved from the borehole (along with the core tube and a core sample therein), and the control unit 12 then coupled to the downhole unit 11 as previously described, orientation data recorded by the downhole unit 11 is transmitted wirelessly to the control unit 12 through operative cooperation between the two IR interfaces 68, 95. The control unit 12 receives and processes orientation data from the downhole unit 11 and provides an indication of the orientation of a core sample within the core tube at a time prior to separation of the core sample from the underground environment from which it was obtained.

The orientation system 10 operates in a fashion similar to that described in aforementioned international application PCT/AU2005/001344 (WO 2006/024111), the contents of which are incorporated herein by way of reference. In particular, the triaxial accelerometer means 85 comprises three internal silicon accelerometers operating along orthogonal directions X, Y and Z. The three accelerometers measure components of the earth's gravitational field. Mathematically transforming the outputs from the three accelerometers allows the rotational orientation of the downhole unit 11 about its longitudinal axis to be determined. More particularly, the signals produced by the triaxial accelerometer means 85 are determinative of the change in orientation of the downhole unit and are transmitted to the analogue-to-digital converter 87 which in turn transmits signals or signal data to the microcontroller 89. The microcontroller 89 processes signals from the arrangement over predetermined time intervals.

When the downhole unit 11 is operational, the relative orientation of the tool is determined at regular time intervals by the processing means 89[. The processed data is stored in the memory of the memory device 91. In this embodiment, the time intervals at which the orientation is determined and stored comprises intervals of one minute, although other intervals are of course possible.

The watchdog circuit 93 is provided for watching the system. In instances where the downhole unit 11 shuts down while in the borehole, it can be reset at the surface. Similarly, the control unit 12 has the watchdog circuit 79 for resetting as necessary.

A calibration unit 97 (as shown in FIG. 6) is provided for calibrating the downhole unit 11 as required to maintain its accuracy. The calibration unit 97 is configured to incorporate a spigot formation 98 for engagement with the socket formation 25 of the downhole unit 11.

A docking station 99 (as shown in FIG. 7) is provided for supporting the control unit 12 when it is not in use and for charging the power supply 67 as necessary. The docking unit 99 incorporates a socket formation 101 for receiving the spigot formation 27 on the control unit 12.

The following process occurs in the operation of the downhole unit 11 connected to the core tube. A first step comprises activating the downhole unit 11 and establishing a reference time. The core drill having the core tube is moved down the borehole to a drilling location at which it is operated to drill a core sample. While the core drill is moved to the drilling location, and also while it is operating, the downhole unit 11 generates acceleration signals associated with the rotational orientation of the downhole unit 11 and the core tube to which it is attached. The processing means 89 then processes the signals to provide processed data from which a measure of rotational orientation of the downhole unit 11 at the drilling location can be established. The processed data is stored in memory device 91 for later recall such that the measure of the rotational orientation of the downhole unit can be obtained therefrom.

During the drilling operation, a core sample is progressively generated within the core tube. When the core sample is to be extracted, the core drill operator refers to a timer and notes or records the duration of time since the downhole unit was activated at the commencement of operation. Specifically, the operator either notes the full minute that has previously elapsed or waits until the next full minute elapses, and then records that time (as it must be recalled later). The operator then initiates the procedure for breaking the core sample from the body of material, ensuring that no rotation of the core tube occurs. The core tube is retrieved from the drill hole in the conventional manner.

When the core tube and the downhole unit 11 is at the surface, the control unit 12 is coupled to the downhole unit 11 in the manner previously explained. The coupling 23 allows the control unit 12 to be selectively rotated with respect to the downhole unit 11 to establish the desired orientational relationship therebetween. This will, of course, require application of a rotational force between the downhole unit 11 and the control unit 12 sufficient to over-ride the magnetic attraction therebetween to permit the relative rotation to occur.

The orientation data collected by the downtool tool 11 is transmitted wirelessly to the control unit 12 through the IR interfaces for subsequent interrogation of the orientation data. The time reading recorded previously is entered into the control unit by way of the keyboard input device 69. The orientation data is processed in relation to the time entry to determine the orientation of the downhole unit 11 (and hence the core tube and the core sample confined in the core tube) prior to breaking the core sample from the body of material. By using integration means and the prescribed time intervals the processed data is indicative of the change orientation of the downhole unit in the prescribed time intervals commencing from the reference time corresponding to the time at which the downhole unit was activated.

The control unit 12 processes the orientation data and provides a measure of the target orientation of the downhole unit 11 in relation to the current rotational orientation thereof. This allows for the downhole unit 11 to consequently be rotated to reflect the measure of the orientation of the core orientation device. The visual display device 71 displays a visual indication of the direction in which the downhole unit 11 and the core tube attached thereto should be rotated to attain the target orientation. Rotating the downhole unit 11 and the core tube attached thereto in the indicated direction causes the core sample contained within the core tube to move into the target orientation (corresponding to the orientation of the core sample at the time that the core sample was in the underground environment before extraction).

Once the required target orientation has been attained, the core sample within the core tube can be marked as necessary and then withdrawn from the core tube.

In this embodiment, the visual indication comprises a directional arrow arrangement showing the required rotational direction. Once the downhole unit is at the target orientation, the display may provide an image representing that condition. Other visual arrangements are, of course, possible. Further, the indication need not necessarily be a visual indication; for example, the indication may comprise any appropriate sensory indication including visual, audible, and tactile indications, as well as any combination thereof. Further, the nature of the indication may vary as the orientation of the rotating downhole unit approaches the target orientation. A visual indication may, for example, comprise a flashing signal which increases in frequency as the target orientation is approached. Similarly, an audible signal may comprise a series of discrete audible tones which increase in frequency as the target orientation is approached, or alternatively a continuous audible signal which varies in tone as the target orientation is approached.

Referring now to FIGS. 10 to 16, there is shown a core sample orientation system 110 according to the second embodiment. The core sample orientation system 110 is similar in some respects to the core sample orientation system 10 according to the first embodiment and so corresponding reference numerals will be used to identify corresponding parts. The corresponding parts in the core sample orientation system 110 will not necessarily be described further.

In particular, the core sample orientation system 110 comprises downhole unit 11 and control unit 12 which feature coupling 23 therebetween. The coupling 23 comprises a combination of a magnetic connection and a mechanical connection.

The core sample orientation system 110 is designed for use in conjunction with a downhole assembly 111 comprising a core tube 113, a back-end portion 115 and a housing 117 installed between the core tube 113 and the back-end portion 115. The back-end portion 115 is of standard wire line construction and is normally connected directly to core tube 113; however, in this embodiment, the housing 117 is configured for installation between the core tube 113 and the back-end portion 115.

The housing 117 may be of a construction as described in the applicant's Australian Provisional Patent Application 2009900590 and corresponding international application filed under the Patent Cooperation treaty, the contents of both of which are incorporated herein by way of reference.

In the arrangement shown, the housing 117 incorporates a compartment 119 configured to accommodate the downhole unit 11. The downhole unit 11 is confined in the compartment 119 to move in unison with the housing 117, both in translation and rotation.

The housing 117 has a bottom end 121 adapted for connection to the upper end of the core tube 113, and an top end 123 adapted for connection to the back-end portion 115.

In this way, the downhole unit 11 is also connected to the core tube 113 so that it record data relative to the orientation of the core tube and any core sample contained therein.

The housing 117 comprises two parts, being lower body part 125 and an upper cap part 127. The two parts 125, 127 cooperate to define the compartment 119 for accommodating the downhole unit 11. The parts 125, 127 are selectively separable to provide access to the compartment 119. In the arrangement illustrated in FIG. 15, the two parts 125, 127 are shown in the separated condition.

The lower body part 125 has an end 131 configured as a spigot 133, and the upper cap portion 127 has an adjacent end configured as a socket 137 in which the spigot 133 can be threadingly received to secure the two parts together. A sealing means 139 is provided to effect fluid-tight sealing engagement between the two parts 125, 127. In the arrangement illustrated, the sealing means 139 comprises O-rings on the spigot 133.

The housing 117 is configured to enable fluid to flow past the downhole assembly 111 as it descends within a borehole (or more particularly within the drill rods within the borehole). Preferably, the arrangement is such that the fluid can flow past the descending downhole assembly 111 at a rate sufficient to allow the assembly to descend rapidly.

The end 131 of the lower body part 125 configured as a spigot 133 is also configured as a socket formation 141 which performs a function similar to that of the socket formation 25 of the core sample orientation system 10 according to the first embodiment. Specifically, the socket formation 141 is adapted to receive the spigot formation 27 on the control unit 12. The spigot formation 27 and the socket formation 141 cooperate to provide the mechanical connection established by the coupling 23.

The end 143 of the downhole unit 11 adjacent the socket formation 141 presents an inner face 145 which incorporates a magnetic element 149. The magnetic element 149 cooperates with the magnetic element 43 on the spigot formation 27 on the control unit 12 to establish the magnetic attractive force between the two portions 11, 12 when the spigots formation 27 is received within the socket formation 141. This arrangement provides the magnetic connection established by the coupling 23.

In FIG. 10, the control unit 12 is shown coupled to downhole unit 11 while the lower body part 125 is within a drill string. This is merely for illustrative purposes only to show that the housing 117 and the overall assembly 111 can be received within the drill string. Typically, the assembly 111 is withdrawn from the drill string before the two parts 125, 127 are separated and the control unit 12 is connected to the downhole unit 11.

Operation of the downhole assembly 111 will now be described. The housing 117 is installed between the core tube 113 and the back-end portion 1115, as previously described to provide the assembly 111.

The two parts 125, 127 of the housing 117 are separated to allow installation of the downhole unit 11 into the compartment 119 and then coupled together to encase the downhole unit 11 within the compartment 119.

The assembly 111 is then lowered down the drill rods within the borehole in conventional manner. As the assembly 111 descends, fluid within the drill rods flows upwardly (relative to the descending assembly 111). Fluid within the drill rods is able to flow past the housing 117 as it descends within the drill rods and so the presence of the housing does not restrict fluid flow to such an extent to inhibit relatively rapid descent of the assembly 111.

At the completion of the core drilling operation, the core sample is retrieved in known manner. Once the assembly 111 is at ground level, the two parts 125, 127 of the housing 117 can be separated to provide access to the downhole unit 11 within the lower body part 125. The control unit 12 can then be brought into cooperation with the downhole unit 11, as shown in FIG. 10, to receive and process the orientation data received from the downhole unit 11. Specifically, the socket formation 141 on the lower body part 125 receives the spigot formation 27 on the control unit 12. The spigot formation 27 and the socket formation 141 cooperate to provide the mechanical connection established by the coupling 23. Further, the magnetic element 149 on end 143 of the downhole unit 11 within the lower body part 125 cooperates with the magnetic element 43 on the spigot formation 27 on the control unit 12 to provide the magnetic connection established by the coupling 23.

The coupling 23 allows the control unit 12 to be selectively rotated with respect to the downhole unit 11 to establish the desired orientational relationship therebetween, as was the case with the first embodiment.

Once the orientation of the core sample within the core tube 113 has been established and recorded, the core sample can be removed from the core tube. The two parts 125, 127 of the housing 117 can then be brought together again to encase the downhole unit 11 within the housing so that the next core sampling operation can be performed when required.

From the foregoing it is evident that the present embodiments each provides a modular core sample orientation system involving the downhole unit 11 and the control unit 12 as separate parts. Because the control unit 12 is separate from the downhole unit 11 and is not deployed in the borehole during the core sampling operation, it is isolated from the rigours to which the downhole unit 11 is exposed during deployment. Similarly, the control unit is isolated from the rigours to which unitary core orientation tools (such as the tool disclosed in aforementioned international application PCT/AU2005/001344) are exposed when in boreholes.

Modifications and improvements may be made without departing from the scope of the invention. For example in other embodiment the physical orientation need not comprise a rotational orientation but rather a measure of degrees above or below the horizontal plane.

Throughout the specification and claims, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. 

1. A core orientation system comprising a first portion adapted for cooperation with a core tube for recording data relating to the orientation of the core tube, and a second portion adapted to cooperate with the first portion to receive and process orientation data from the first portion and provide an indication of the orientation of a core sample within the core tube at a time prior to separation of the core sample from the underground environment from which it was obtained, the first and second portions being adapted for cooperation in a manner allowing selective rotation therebetween.
 2. The core orientation system according to claim 1 wherein the first portion is adapted for cooperation with a core tube by being adapted for connection to the core tube for rotational movement in unison therewith.
 3. The core orientation system according to claim 2 wherein first portion is adapted for direct connection with the core tube.
 4. The core orientation system according to claim 3 wherein first portion is adapted to be accommodated within a housing adapted for connection to the core tube.
 5. The core orientation system according to claim 1, further comprising a coupling for releasably coupling the two portions together.
 6. The core orientation system according to claim 5 wherein the coupling is so configured that the second portion can dock onto the first portion.
 7. The core orientation system according to claim 5 wherein the coupling is configured to allow selective rotation of the second portion relative to the first portion.
 8. The core orientation system according to claim 5, wherein the coupling comprises a mechanical coupling.
 9. The core orientation system according to claim 5 wherein the coupling comprises a magnetic coupling.
 10. The core orientation system according to claim 5 wherein the coupling comprises a combination of magnetic coupling and mechanical coupling.
 11. The core orientation system according to claim 8, wherein the mechanical coupling comprises a spigot formation associated with one of the two portions and a corresponding socket formation associated with the other of the two portions for providing alignment between the two portions when the spigot formation is received within the socket formation.
 12. The core orientation system according to claim 11 wherein the magnetic coupling comprises an attractive force between the two portions for biasing the spigot formation and the socket formation into engagement.
 13. The core orientation system according to claim 11 wherein the spigot formation is provided on the second portion and the corresponding socket formation may be associated with the first portion.
 14. The core orientation system according to claim 13 wherein the corresponding socket formation is provided in the first portion.
 15. The core orientation system according to claim 13 wherein the corresponding socket formation is provided in a member associated with the first portion.
 16. The core orientation system according to claim 15 wherein the member comprises a housing accommodating the first portion.
 17. The core orientation system according claim 16 wherein the housing at least two parts adapted for connection together and selectively separable to provide access to the first portion accommodated therein.
 18. The core orientation system according to claim 1 wherein orientation data is transmitted from the first portion to the second portion by wireless communication.
 19. The core orientation system according to claim 1 wherein the first portion comprises a downhole unit and the second portion comprises a control unit.
 20. A core orientation system comprising a first portion for recording orientation data and a second portion adapted to cooperate with the first portion to receive and process orientation data from the first portion, the first and second portions being adapted for cooperation in a manner allowing selective rotation therebetween.
 21. A survey tool system comprising a housing and a core orientation system, wherein the core orientation system comprises a first portion for recording data relating to the orientation of a core sample, and a second portion adapted to cooperate with the first portion to receive and process orientation data from the first portion and provide an indication of the orientation of the core sample at a time prior to separation of the core sample from the underground environment from which it was obtained, the first portion being contained within the housing, the housing comprising at least two parts adapted for connection together and selectively separable to permit the second portion to access the first portion for cooperation therebetween.
 22. A survey tool system comprising a housing, a downhole unit for recording data relating to the orientation of a core sample, and a control unit adapted to cooperate with the downhole unit to receive and process orientation data from the downhole unit and provide an indication of the orientation of the core sample at a time prior to separation of the core sample from the underground environment from which it was obtained, the downhole unit being contained within the housing, the housing comprising at least two parts adapted for connection together and selectively separable to permit the control unit to access the downhole for cooperation therebetween.
 23. A method of providing an indication of the orientation of a core sample relative to a body of material from which the core sample has been extracted, the method being performed using an orientation system according to claim
 1. 24. A method of providing an indication of the orientation of a core sample relative to a body of material from which the core sample has been extracted, the method being performed using an tool survey system according to claim
 21. 25.-26. (canceled) 